Using the phytohemagglutinin-stimulated human lymphocyte as a model system, the proposed research will continue on-going studies of the role of zinc in cell growth and cell differentiation. Studies will be concluded in which transferrin-bound zinc incorporated by stimulated lymphocytes is localized in various subcellular compartments by subcellular fractionation techniques. Additionally, studies will be initiated in which column chromatography and electrophoresis are employed to identify the number and gross nature of proteins in the various subcellular fractions (i.e., nuclei, mitochondria, microsomes, and cytosol) associated with incorporated radioactive 65-zinc. The proposed research will also attempt to determine if the lymphocyte synthesizes a cytoplasmic zinc-binding protein in response to mitogenic stimulation using both gel filtration and electrophoretic techniques. Finally, using lymphocytes which have incorporated transferrin-bound radioactive 65-zinc, accepted protocols for the isolation of key cellular enzymes (RNA polymerases, DNA polymerases, and alkaline phosphatase) will be followed to see if 65-zinc activity corresponds with each of the respective enzyme activities.